This research is directed toward developing means of utilizing magnetic microspheres to rapidly and reliably separate target cells. Initially, the target cell will be peripheral blood T lymphocytes, and the work will evaluate the ability to deplete this cell population. Later, the system will be applied to bone marrow toward the goal of eliminating graft versus host disease (GVHD). Removal of T lymphocytes from donor marrow has been shown to greatly reduce or eliminate GVHD. Phase I will study two different magnetic microspheres coupled to two different antibodies by various means for T-lymphocyte removal. T-lymphocyte removal, as judged by E-rosetting and fluorescent tagging, will indicate which microsphere-antibody coupling methods are the most efficient and cost effective. Phase II will test the method(s) selected in Phase I for T-lymphocyte removal from normal donor marrow by biological assays and E-rosetting and fluorescent tagging. The colony forming ability of stem cells will be determined to assess marrow viability. The method(s) of choice will then be tested in patients. This research is designed to lead to a method for preventing CBHD that can be used in a clinical setting. (TT)